DE10137620A1 - Adhesive tape, in particular for packaging purposes - Google Patents

Abstract

Adhesive tape equipped on one side with DOLLAR A a. a film based on thermoplastic polymers, DOLLAR A b. an adhesive layer applied on one side to the film, made from a mixture containing DOLLAR A 35 to 69.5% by weight a natural rubber latex DOLLAR A 20 to 64.5% by weight a resin dispersion based on a hydrocarbon resin DOLLAR A 0.5 to 20% by weight of an oil-based additive DOLLAR A 0.001 to 3% by weight of a defoamer based on an organomodified polysiloxane.

Description

The invention relates to an adhesive tape with a carrier based on thermoplastic polymer based on one side with a solvent-free adhesive is coated by natural rubber latex, as well as the use of the adhesive tape as Packaging tape.

Adhesive tapes with foils based on polyolefins, such as, for example, biaxially oriented Polypropylene, and adhesives based on solvent-based natural rubber or aqueous acrylate dispersions are known and are from known manufacturers offered.

A description is for example in "Packaging Tapes", Stefan Röber in "Handbook of Pressure Sensitive Adhesive Technology", Third Edition, edited by Donatas Satas, Satas & Associates, Warwick, Rhode Island pp. 787-814. More descriptions are found in "European Adhesives & Sealants" 10 (4), 1993, 29 by G. Pedala and "European Adhesives & Sealants" 2 (2), 1985, 18 by R. W. Andrew.

Due to the known disadvantages in the production of solvent-based adhesive tapes, such as the elaborate recycling of solvents, the emission of Solvents into the environment, the hazard in the workplace due to highly flammable Solvent and the limitation of the coating speed by drying the adhesive, are solvent-free technologies for the production of adhesive tapes progressive importance.

In addition to the problem of solvent technology already described, the required degradation of the natural rubber in the manufacture of the adhesive, the Mastication. This results in a significantly reduced cohesiveness of the adhesive depending on Strength of degradation due to mechanical stress.

The targeted, technical process of rubber mining under the combined action of shear stress, temperature, atmospheric oxygen is in the Technical literature referred to as mastication and mostly in the presence of chemical Aids carried out from the specialist literature as masticating agents or peptizers, are less commonly known as "chemical plasticizers".

The mastication step is necessary in rubber technology to facilitate the To achieve absorption of the additives.

The mastication is a rubber technology term for the degradation of long-chain Rubber molecules to increase the plasticity or reduce the (Mooney) viscosity of rubbers. The mastication is carried out by Treatment in particular of natural rubber in kneaders or between rollers temperatures as low as possible in the presence of mastication aids (Masticating). The high mechanical forces that act lead to one "Tearing" the rubber molecules to form macro radicals, the Recombination is prevented by reaction with atmospheric oxygen. Mastication aids, such as aromatic or heterocyclic mercaptans or their zinc salts or Disulfides, accelerate the process by promoting the formation of primary radicals Mastication. Activators, such as metal (iron, copper, cobalt) salts of Tetraazaporphyrins or phthalocyanines allow a reduction in the Mastication. Mastication aids are used in the mastication of natural rubber Quantities of about 0.1 to 0.5 wt .-% used in the form of masterbatches, the one even distribution of this small amount of chemicals in the rubber mass facilitate.

The mastication is to be distinguished strictly from that of all usual, solvent-free polymer technologies such as compounding, conveying and coating in the Melting resulting degradation, the degradation.

Degradation is a collective name for different processes that Change the appearance and properties of plastics. Degradation can lead to Example through chemical, thermal, oxidative, mechanical or biological influences or caused by exposure to radiation (such as (UV) light). The result is Example oxidation, chain splitting, depolymerization, crosslinking respectively Cleavage of side groups of the polymers. The stability of polymers against one Degradation can be caused by additives, for example by adding stabilizers, such as Antioxidants or photo stabilizers, can be increased.

The use of strongly degraded adhesives based on Natural rubber hot melt pressure sensitive adhesives for adhesive tapes, in particular packaging adhesive tapes, for sealing Cardboard boxes made from recycled paper or cardboard boxes cause the cardboard boxes to move out early to open. If the carton has sufficient lid tension, caused by the Filling pressure of the packaged material in the box or by closing counteracting tension of the packaging material, the tape detaches from the Carton surface, and the carton opens by sliding the Packing tape.

Packaging tapes for cardboard boxes can therefore not be made with a nozzle coated adhesive based on natural rubber. The cohesion such masses are not sufficient. When using adhesives based on Natural rubber latex, i.e. water-based natural rubber, eliminates any type of mechanical degradation of the rubber. The adhesives are therefore characterized by excellent cohesion.

The cohesion and thus the packaging security of adhesive tapes with an adhesive based on natural rubber can either by crosslinking the rubber adhesive and / or by a production variant of the adhesive, in which the one used Natural rubber is significantly less degraded and therefore a higher one Has molecular weight can be improved. This can cause the Adhesive tapes on the cardboard surface can be counteracted as described above.

Solvent-free technologies for the production of adhesive tapes, in particular Packaging adhesive tapes, has so far been based on the use of adhesive Acrylic dispersions and the use of melting, thermoplastic Limited elastomers.

Advantage of these thermoplastic elastomers, mainly block copolymers with Polystyrene blocks, is the relatively low softening point and the associated Simplifying the application or painting process and avoiding the above Disadvantages of the solvent-based technologies described.

Other solvent-free systems based on aqueous adhesives, such as Adhesive systems based on polyvinyl acetate, polyvinyl acetate-ethylene copolymers, neoprene, Styrene-butadiene, polyurethane, polyvinyl alcohol, due to the use of adhesive tapes, in particular packaging tapes, unfavorable costs and / or performance structure little or no application.

An overview of the most important, aqueous adhesive systems and their use can be found in "Solvent free adhesives", T. E. Rolando (H. B. Fuller) in "Rapra Rev. Rep.", 1997, 9 (5), 3-30 Rapra Technology Ltd.

Different ways of solvent-free production and processing of rubber Pressure sensitive adhesives are known.

An overview of such adhesives and their use in the field of pressure Sensitive Adhesives can be found in "Natural Rubber Adhesives" (G. L. Butler in "Handbook of Pressure Sensitive Adhesive Technology ", Third Edition, edited by Donata Satas, Van Nostrand Reinhold New York, pp. 261-287).

All known processes are characterized by extremely strong rubber degradation. This requires extreme processing of the masses into self-adhesive tapes Networking conditions and also has a partially restricted Application profile, especially for the use of resulting self-adhesive tapes at higher ones Temperatures, as a result. Solvent-free hotmelt pressure-sensitive adhesive based on non- thermoplastic elastomers, such as natural rubber or others high molecular rubbers, have one for the without crosslinking step of the adhesive Most applications have insufficient cohesion and are therefore not used in the context of a packaging tape. Cause of this failure of uncrosslinked adhesive based on natural rubber is the relatively strong reduction in Molecular weight through processing or through the manufacturing process the adhesive compositions based on natural rubber and the resulting reduced or insufficient cohesion of the adhesives.

CA 698 518 describes a process of how mass production can be achieved by adding large amounts of plasticizer and / or at the same time strongly masticating the rubber. It is true that this process can be used to achieve pressure sensitive adhesives with extremely high grip strength; Due to the relatively high proportion of plasticizer or the strong degradation of the molecular structure of the elastomer to a molecular weight average of M _w ≤ 1 million, the user-friendly shear strength can only be achieved to a limited extent even with subsequent, higher crosslinking.

The use of polymer blends in which in addition to non-thermoplastic Natural rubber block copolymers are used in a ratio of approx. 1: 1 essentially an unsatisfactory compromise solution, since neither high Shear strengths when using the self-adhesive tapes at higher temperatures, yet significant improvements over the properties described in CA 698 518 result.

Raw natural rubber latex is supplied by the plantations and by means of appropriate Methods cleaned, preserved and concentrated. The are generally described Latex types and methods of processing in "Natural rubber - technical Information Sheet ", Malaysian Rubber Producers Research Association, L1, 1977 and in "Rubber technology", Werner Hofmann, Gentner-Verlag, Stuttgart p. 51ff.

• 1. Standard-Naturkautschuklatex mit einem hohen Ammoniakgehalt von 0,7 Gew.-%;
• 2. Naturkautschuklatex mit niedrigem Ammoniakgehalt von 0,2 Gew.-% in Kombination mit Zinkoxid und Tetramethyl-thiuram-dissulphid < 0,035 Gew.-%;
• 3. Naturkautschuklatex, doppelt zentrifugiert mit besonders hoher Reinheit;
• 4. Naturkautschuklatex, teilweise vulkanisiert für spezielle Anwendungen:

Natural rubber latex is harvested as a natural product from so-called latex trees. After various preparation steps for separation and cleaning, four basic types of natural rubber latices are distinguished:

• 1. Standard natural rubber latex with a high ammonia content of 0.7% by weight;
• 2. Natural rubber latex with a low ammonia content of 0.2% by weight in combination with zinc oxide and tetramethylthiuram dissulphide <0.035% by weight;
• 3. Natural rubber latex, double centrifuged with particularly high purity;
• 4. Natural rubber latex, partially vulcanized for special applications:

Mastication and the associated degradation of the natural rubber is not necessary in the production of adhesive compositions based on natural rubber latex, since in the case of the solvent-free, aqueous adhesive composition, simply mixing the components means that there is no mastication and thus no molecular degradation due to mechanical stress. This results in a tight entanglement of the natural rubber latex / isoprene molecules, a high molecular weight due to the lack of mastication, a broad molecular weight distribution and a low softening point T _g .

These factors result in a very good balance between cohesion and adhesion Resin blends resulting adhesive and continue to be extremely useful for tapes powerful property profile over a very wide temperature range.

The production of aqueous adhesive compositions based on natural rubber latex is known. As described above, these adhesives are used to produce self-adhesive Labels used. The usual methods for the production of Dispersion adhesives used.

Also the production of adhesive systems, which are natural rubber latex included, described in EP 0 960 923 A1. On the one hand, the production of Dispersion adhesives also disclose the incorporation of natural rubber latex into other natural rubber adhesive systems using kneaders, mixers or extruders. This way Adhesives produced can be coated on foils or nonwovens.

An improvement in the packaging properties of such adhesive tapes by means of a controlled, sustainable networking of the adhesive, which is also part of a meaningful production process can not be used is not described.

When using adhesive compositions based on natural rubber latex - how already mentioned above - sustainable networking is not necessary to achieve a good to achieve superior packaging behavior in most other adhesive systems.

Through the use of the stabilizing resin dispersions described above and through Use of natural rubber latex and thus the absence of any mechanical Rubber degradation is a manufacture, processing and coating of adhesives Basis of natural rubber latex possible and thus the production of adhesive tapes because the adhesive has a very high cohesion and therefore optimal packaging security having.

Not only for packaging tapes to close the carton, but also for others Packaging tapes, such as strapping tapes, are therefore sufficient cohesion Adhesive based on natural rubber necessary.

This positive behavior over a wide temperature range is exploited in the JP 56 030 481 A1 described adhesive tape with an adhesive based on Natural rubber latex. The use of natural rubber latex makes it shock-resistant Behavior at low temperatures described.

Another point is that natural rubber latex is characterized by a particularly wide range of applications. So natural rubber latex is on the one hand for use as Adhesive suitable for packaging materials and secondly for applications outside of adhesive technology.

A disadvantage of adhesive systems based on natural rubber latex is the lack of Stability of the raw material natural rubber latex against mechanical stress and the associated coagulation of the natural rubber latex in the adhesive. This Shear sensitivity results in the limited manageability and usability of the Natural rubber latex for the adhesive technology and adhesive tape industry. The Production of adhesive tapes in which the adhesive composition containing the natural rubber latex is included can be coated on a film at high speed is not yet known.

Through the use of stabilizing resin dispersions and / or surface-active Substances, such as emulsifiers, can affect the stability of the natural rubber latex be significantly increased. With the increase in the stability of the natural rubber latex Surfactants in high concentrations are at the same time a loss of Coupled cohesion of the adhesive, so that here a balanced balance between Stabilization and sufficient cohesion must be found.

The general use of natural rubber latex for adhesives and latex Stabilizing resin dispersions are described in "Tackified waterborne adhesive for PSA tapes ", J.G. de Hullu, European Adhesive & Sealants, 12 (1998), pp 11-12 Use of such resin dispersions stabilizing the natural rubber latex becomes one Processing or coating of adhesives based on Natural rubber latex enables. The trouble-free application of the Dispersion adhesives on a polymeric carrier are technically feasible and economical sensible tape production possible. The use of a suitable composition the adhesive and the technical adjustment and optimization of the coating systems allow the use of this technology.

The use of defoaming additives in aqueous adhesives is state of the art. In particular, defoamers based on mineral oil, modified ones Fatty acids and fatty alcohols, from polyethers and silicones use. defoamers may be necessary when using aqueous adhesives to make one for the Standard production to ensure sufficiently low foaming.

What these defoamers have in common is that, due to their special, surface-active Effect in either a variety of aqueous adhesive systems is good have defoaming action or sufficient wettability of the aqueous Ensure adhesive on polymeric surfaces, such as polypropylene. A at the same time good anti-foaming and good wettability of the adhesive on polymers Surfaces cannot be achieved with these types of defoamers.

With a suitable defoaming effect, craters form when the aqueous is spread out Adhesive on polymer surfaces.

Therefore, the use of specially modified defoamers for aqueous Adhesives that have a sufficient defoaming effect and a sufficient Generate wetting of the adhesive on polymer surfaces, not previously known.

The application and development of an adhesive tape that rolls off quietly and for Suitable for packaging applications is not described by J.G. de Hullu. The Use of quietly unrolling adhesive tapes, especially for sealing cartons however of great importance within the packaging industry to reduce noise pollution in to lower the packaging halls and thus increase the work output. The Quiet roll ability is fundamental to packaging tape to be classified in the middle to upper price / performance segment.

Packaging tapes for carton closure are used in the packaging industry applied by machine or manually. This is especially in large packaging lines and halls the quiet, non-rattling rolling behavior an additional advantage of Packaging tapes to make working more pleasant. This is a essential quality feature for packaging tapes in Europe.

Here, with quietly running adhesive tapes, at a distance of 25 cm, less measured as 80 dB (A) while loud, crackling packaging tapes achieve significantly higher dB (A) values.

• - lösemittelhaltigem Naturkautschuk a),
• - einem Styrol-Isopren-Styrol-Schmelzhaftkleber b) und
• - einer wasserbasierenden Acrylatdispersion c)
  • a) Polypropylenbasierende Verpackungsklebebänder mit einer Klebemasse auf Basis von lösemittelhaltigem Naturkautschuk laufen bei entsprechender Masse leise ab. Hierzu ist eine weiche, flexible Masse notwendig. Meistens jedoch sind derartige Klebebänder mit einer lösemittelhaltigen Carbamatlackierung versehen, um die Abrollkraft zu reduzieren. Die Rückseitenlackierung führt dazu, daß das Klebeband laut und knatternd abrollt.
  • b) Polypropylenbasierende Verpackungsklebebänder mit einer Klebemasse auf Basis von Styrol-Isopren-Styrol-Schmelzhaftklebern können nur in Verbindung mit einer geeigneten Rückseitenlackierung eingesetzt werden. Ohne Rückseitenlackierung ist bedingt durch die chemische Struktur der Masse die Abrollkraft des Klebebandes so hoch, daß der Träger beim Abrollen geschädigt wird und somit die Verpackungseigenschaften stark herabgesetzt werden. Die Rückseitenlackierung, meist lösemittelhaltige Carbamatlackierungen, führen dazu, daß das Klebeband extrem laut und knatternd abrollt.
  • c) Polypropylenbasierende Verpackungsklebebänder mit einer Klebemasse auf Basis von wasserbasierenden Acrylaten werden in Kombination mit einer Coronabehandlung der Rückseite, der Klebemasse abgewandten Trägerseite, eingesetzt. Ohne entsprechende Coronabehandlung der Rückseite laufen diese Klebebänder laut und knatternd ab. Mit entsprechend eingestellter Coronabehandlung der Rückseite kann ein leises und knatterfreies Ablaufen der Verpackungsklebebänder erreicht werden.
    Dies wird in der EP 0 096 841 A1 beschrieben. Durch diese Coronabehandlung der Trägerrückseite, zum Beispiel nach der Beschichtung während des Schneidprozesses, wird die Abrollkraft der Klebebänder erhöht und somit ein Abplatzen der Klebemasse vom Träger verhindert. Dieses Abplatzen der Klebemasse vom Träger auf Grund des Abrollvorganges führt zu einem lauten, knatternden Abrollverhalten. Mittels der Coronabehandlung der Rückseite in geeignetem Maß wird das Klebeband leise abrollend. Hierbei wird durch geeignete Coronabehandlung der Rückseite die Abrollkraft eingestellt und somit auch das Abrollverhalten eingestellt. Bis zum heutigen Entwicklungsstand sind alle Klebebänder ohne Rückseitencoronabehandlung laut abrollend.
    Die Coronabehandlung der Klebebänder bringt im wesentlichen Nachteile mit sich. Zum ersten ist ein zusätzlicher Arbeitsschritt verbunden, der eine zusätzliche, maschinelle Ausrüstung verlangt. Im Falle der Coronabehandlung beim Schneidprozeß können nur Schneidmaschinen mit einer Schneidcorona verwendet werden. Dies erfordert teilweise zusätzliche, maschinelle Anschaffungen. Zum zweiten ist die genaue Stärke der Coronabehandlung entscheidend, um den gewünschten Effekt zu erzielen. Dies bringt eine große Prozeßunsicherheit mit sich, die zu verstärkter Qualitätskontrolle verpflichtet.
    Im Fall einer zu geringen Coronaleistung wird der gewünschte Effekt des leisen Abrollens nur unzureichend erfüllt, und da die resultierenden, fertigen Klebebänder nicht nachbehandelt werden können, ist die Produktion von Ausschuß die Folge. Im Fall einer zu starken Coronaleistung wird die Abrollkraft zu stark erhöht, wodurch es zu einer Trägerüberdehnung, einem Trägerabriß oder zu einem Übergang der Klebemasse während des Abrollens des Klebebandes kommt.

Adhesive tapes currently on the market with a backing based on stretched polypropylene can be divided into the following variants, depending on the adhesive:
Adhesive tapes with an adhesive based on:

• - solvent-containing natural rubber a),
• - A styrene-isoprene-styrene hot melt pressure sensitive adhesive b) and
• - a water-based acrylic dispersion c)
  • a) Polypropylene-based packaging tapes with an adhesive based on solvent-based natural rubber run quietly with the appropriate mass. This requires a soft, flexible mass. Most of the time, however, such adhesive tapes are provided with a solvent-based carbamate coating in order to reduce the unwinding force. The back coating leads to the tape rolling off loudly and rattling.
  • b) Polypropylene-based packaging tapes with an adhesive based on styrene-isoprene-styrene hotmelt pressure-sensitive adhesives can only be used in conjunction with a suitable back coating. Without rear coating, the chemical structure of the mass means that the unrolling force of the adhesive tape is so high that the carrier is damaged when unrolling and the packaging properties are thus greatly reduced. The back coating, mostly solvent-based carbamate coatings, cause the tape to roll extremely loud and crackling.
  • c) Polypropylene-based packaging tapes with an adhesive based on water-based acrylates are used in combination with a corona treatment of the back, the carrier side facing away from the adhesive. Without appropriate corona treatment on the back, these tapes run off loudly and rattling. With the corona treatment on the back set appropriately, the packaging tapes can run quietly and without creasing.
    This is described in EP 0 096 841 A1. This corona treatment of the back of the backing, for example after coating during the cutting process, increases the unwinding force of the adhesive tapes and thus prevents the adhesive from flaking off the backing. This peeling of the adhesive from the carrier due to the unrolling process leads to a loud, crackling unrolling behavior. The adhesive tape rolls off quietly by means of a corona treatment on the back to a suitable extent. In this case, the rolling force is adjusted by suitable corona treatment of the back, and thus the rolling behavior is also adjusted. Up to the current state of development, all adhesive tapes without reverse corona treatment are rolling out loud.
    Corona treatment of the adhesive tapes has essentially disadvantages. The first involves an additional work step that requires additional mechanical equipment. In the case of corona treatment during the cutting process, only cutting machines with a cutting corona can be used. This sometimes requires additional, mechanical purchases. Second, the exact strength of the corona treatment is crucial to achieve the desired effect. This brings with it a great deal of process uncertainty, which requires increased quality control.
    If the corona output is too low, the desired effect of quiet unrolling is insufficiently achieved, and since the resulting finished adhesive tapes cannot be post-treated, the result is rejects. If the corona power is too strong, the unwinding force is increased too much, which leads to an overstretching of the carrier, a tearing of the carrier or to a transition of the adhesive mass during the unrolling of the adhesive tape.

In the production of adhesive tapes with adhesive compositions based on natural rubber both water-based and solvent-based primers are used as adhesion promoters inserted between adhesive and carrier film. These have used adhesion promoters partly an adhesive based on natural rubber applied to the solution cross-linking effect.

Natural rubber latex is generally known as a component for adhesives. The Areas of application of such adhesives based on natural rubber latex are Applications in the field of labels and plaster technology.

Monoaxial and biaxially stretched films based on polypropylene are available in large quantities used for packaging tapes. While for applying one Packaging adhesive tape for the cardboard closure based on biaxially stretched films Polypropylene are preferred, find monoaxially stretched in the area of strapping tapes Polypropylene films use. These are characterized by very high tensile strength and low elongation in the longitudinal direction and are very good for bundling respectively suitable for holding pallets together. When using adhesives, the one have insufficient cohesion or inadequate anchorage of the adhesive on the film, the slipping of the strapping tapes causes the pallets to slip and thus insufficient securing of the pallets. An insufficient anchorage the adhesive on the film leads to a when using cardboard tape early opening of the packed boxes.

Thermoplastic films based on polyvinyl chloride (PVC) are used to manufacture Adhesive tapes used by different manufacturers. Here, films stand out above all based on PET due to its high elongation at break and heat resistance from 130 ° C to 175 ° C and resistance to dilute alkalis and acids. Still own Films based on polyester have a very high abrasion resistance and dielectric strength, are due to the relatively high price compared to films based on polyolefins less common in the field of packaging tapes.

The object of the present invention is to provide adhesive tapes with foils based on thermoplastic polymers and solvent-free, water-based To create adhesives based on natural rubber latex, the adhesive during coating or processing due to low foaming and distinguishes good wetting properties. Furthermore, the tapes should be light and roll quietly.

In addition, the new tapes are intended as packaging tapes for commercially available cardboard boxes are ideally suited.

This task is solved by an adhesive tape as set out in the main claim. The subclaims relate to advantageous developments of the subject matter of the invention. Furthermore, the invention relates to proposed uses of the invention Adhesive tape.

Accordingly, the invention relates to a self-adhesive adhesive tape, with a film based on thermoplastic polymers.

The film is provided on one side with an adhesive layer, made from a mixture containing:

35 to 69.5% by weight of a natural rubber latex
20 to 64.5 wt .-% a resin dispersion based on a hydrocarbon resin
0.5 to 20% by weight of an oil-based additive
0.001 to 3% by weight of a defoamer based on organomodified polysiloxanes (OMS)

Surprisingly and completely unexpected for the expert it turns out that when using organomodified polysiloxanes for the adhesive based on natural rubber latex and a carrier based on thermoplastic polymers very little foaming can be set for the adhesive and still the adhesive shows excellent wetting of the polymeric surface when spreading.

Monoaxially and biaxially stretched films can be used according to the invention as films Based on polyolefins, then films based on stretched polyethylene or stretched Copolymers containing ethylene and / or polypropylene units, if appropriate also PVC films, PET films, films based on vinyl polymers, polyamides, polyester, Polyacetals, polycarbonates

The film preferably consists of stretched polyolefins and / or has a film thickness between 20 and 50 µm.

Monoaxially stretched polypropylene is characterized by its very high tensile strength and low elongation in the longitudinal direction and is used, for example, for the production of Strapping tapes used. Particularly preferred for the production of the invention Adhesive tapes, in particular for bundling and palletizing cardboard boxes and others Goods are monoaxially stretched films based on polypropylene.

The thicknesses of the monoaxially stretched films based on polypropylene are preferred between 25 and 200 µm, in particular between 40 and 130 µm.

Monoaxially stretched films are mostly single-layer; in principle can also multilayer, monoaxially stretched films are produced. Most are known one-, two- and three-layer foils, the number of layers also being chosen larger can be.

Furthermore particularly preferred for the production of the adhesive tapes according to the invention u. a. are used to securely close the carton, are biaxially stretched films based on Polypropylene with a stretch ratio in the longitudinal direction between 1: 4 and 1: 9, preferred between 1: 4.8 and 1: 6 and a transverse stretch ratio between 1: 4 and 1: 9, preferably between 1: 4.8 and 1: 8.5.

The elasticity modules achieved in the longitudinal direction, measured at 10% elongation according to ASTM D882, are usually between 1000 and 4000 N / mm ² , preferably between 1500 and 3000 N / mm ² .

The thicknesses of the biaxially stretched films based on polypropylene are particularly high between 15 and 100 µm, preferably between 20 and 50 µm.

Biaxially stretched films based on polypropylene can be produced using blown film extrusion or be produced by means of conventional flat film lines. Biaxially stretched films both single and multi-layer. In the case of multilayer films, you can Again, the thickness and composition of the different layers will be the same, however various thicknesses and compositions are also known.

Single-layer, biaxial are particularly preferred for the adhesive tapes according to the invention or monoaxially stretched films and multilayer, biaxial or monoaxial films Basis of polypropylene, which has a sufficiently firm bond between the layers have, since delamination of the layers is disadvantageous during use.

The adhesion promoter can adhere to the thermoplastic film based on polyolefins be improved by corona treatment or flame pretreatment, because just that Surfaces of the films based on stretched polyolefins can generally by this known methods, such as corona or flame treatment, are treated. Surface treatments by corona treatment are preferred.

An overview of the methods of surface treatment is given, for example, by Article "Surface pretreatment of plastics for adhesive bonding" / A. Kruse; G. Kruger, A. Baalmann and O.D. Hennemann; "J. Adhesion Sci. Technol.", Vol. 9, No 12, pp. 1611-1621 (1995).

The biaxially stretched films for the adhesive tapes of the invention are on the Mass or facing the possibly present adhesion promoter Side pretreated with corona or flame, but preferably not Surface treated and / or corona or flame pretreated on the mass opposite side.

In a further preferred embodiment of the invention is between the optionally flame or corona treated film and the adhesive layer an adhesion promoter present the good bond of the adhesive with the film and the crosslinking of the Adhesive guaranteed.

The optional bonding agent between the adhesive and the carrier film optimizes the Bond between the layers mentioned.

The layer of the adhesive layer is in particular 10 to 45 g / m2. In a preferred embodiment, the layer application is set from 13 to 28 g / m2.

In a particularly preferred variant, the adhesives contain the Adhesive tapes according to the invention 45 to 60 wt .-% natural rubber latex. Furthermore according to the invention are other natural rubber latices as well as mixtures of different types of Natural rubber latexes.

• a) 0,05 bis 20 Gew.-% mindestens eines Farbpigments
• b) 0,05 bis 10 Gew.-% mindestens eines Stabilisators und/oder
• c) 0,1 bis 5 Gew.-% eines Alterungsschutzmittels

Depending on the application, the adhesive can be added, chosen independently:

• a) 0.05 to 20 wt .-% of at least one color pigment
• b) 0.05 to 10% by weight of at least one stabilizer and / or
• c) 0.1 to 5% by weight of an anti-aging agent

The raw material for the adhesive tapes according to the invention is preferred Standard natural rubber latex with an ammonia content of 0.7 wt .-% used, on the one hand because of mentioned natural rubber latex offers price advantages and, secondly, be relative high ammonia content allows good stabilization of the natural rubber latex. in the natural rubber latex is very suitable for the use of Adhesives for adhesive tapes. Due to the very high molecular weight, the entanglements of the Molecular chains, low glass transition temperature and the lack of mastication in the Manufacture of adhesives, natural rubber latex show adhesives based on Natural rubber latex an excellent balance between adhesion and cohesion.

These properties ensure a very high level of packaging security when used of adhesive tapes with an adhesive based on natural rubber latex, especially for Use of critical cardboard types and low temperatures.

The mechanical stability of the natural rubber latex can be critical with regard to mechanical Be shear loads. This leads to strong, mechanical shear loads Coagulation of the natural rubber latex and thus the lack of processability. Possibilities of adhesive compositions based on natural rubber latex compared to mechanical ones On the one hand, stabilizing loads is the use of stabilizing, suitable ones Resin dispersions and the use of emulsifiers.

The adhesive tapes according to the invention preferably contain natural rubber latex between 30 to 64.5% by weight of the standard natural rubber latex with a high ammonia content.

Aqueous resin dispersions, i.e. H. Dispersions of resin in water are known. manufacturing and properties are described, for example, in "Resin Dispersions", Anne Z. Casey in "Handbook of Pressure Sensitive Adhesive Technology", Second Edition, edited by Donatas Satas, Van Nostrand, Reinhold, New York, pp. 545-566.

Resin dispersions of hydrocarbon resins are also known and will be for example offered by Hercules BV under the trade name Tacolyn.

Resin dispersions based on are used for the adhesive tapes according to the invention Hydrocarbon resins or modified hydrocarbon resins as the main resin component used. The adhesive contains between 35 and 69.5% by weight of the resin dispersion and preferably between 40 to 55% by weight of the resin dispersion. The solids content of the Resin dispersion is in particular between 40 and 69.5% by weight, preferably between 45 and 60% by weight.

The use of resin dispersion based on mixtures is also according to the invention various hydrocarbon resins and mixtures of inventive Hydrocarbon resins with other resins.

Resin dispersions based on modified hydrocarbons are also known, and of particular interest here are C5 / C9 hydrocarbon resin dispersions, which are modified with aromatics. This can be due to the proportion of the aromatic content the polarity of the resin dispersion and thus the adhesive can be adjusted. In addition to the The polarity of the adhesive affects the hardness of the resin. The lower the Aromatics content, the lower the polarity of the modified Hydrocarbon resin dispersion.

The adhesive tapes according to the invention contain 0.05 to 20% by weight of an oil based additive, especially a mineral oil dispersed in water.

In a preferred embodiment of the adhesive tapes according to the invention, the Adhesive 2 to 12% by weight and in a particularly preferred variant 3 to 10% by weight a mineral oil dispersed in water.

According to the invention, the use of mixtures of different in water dispersed oils and the use of non-dispersed mineral oils.

Furthermore, the use of various oils, such as, for example, is according to the invention Mineral oils, natural oils and synthetic oils. The use is also according to the invention of mixtures of different oils. According to the invention, the use of a aqueous oil dispersion or the direct use of oil together with a suitable Emulsifier system.

The oils of the adhesive compositions according to the invention are advantageously selected from the group of nonpolar lipids. Particularly advantageous oils for the purposes of the present invention are those listed below:

• - Mineralöle, Mineralwachse;
• - Öle, wie Triglyceride der Caprin- oder der Caprylsäure, vorzugsweise aber Rizinusöl;
• - Fette, Wachse und andere natürliche und synthetische Fettkörper, vorzugsweise Ester von Fettsäuren mit Alkoholen niedriger C-Zahl, zum Beispiel mit Isopropanol, Propylenglykol oder Glycerin, oder Ester von Fettalkoholen mit Alkansäuren niedriger C-Zahl oder mit Fettsäuren;
• - Alkylbenzoate;
• - Silikonöle, wie Dimethylpolysiloxane, Diethylpolysiloxane, Diphenylpolysiloxane sowie Mischformen daraus.

The additive based on an oil can advantageously be selected from the following group of substances:

• - mineral oils, mineral waxes;
• - oils, such as triglycerides of capric or caprylic acid, but preferably castor oil;
• - Fats, waxes and other natural and synthetic fat bodies, preferably esters of fatty acids with alcohols with a low C number, for example with isopropanol, propylene glycol or glycerol, or esters of fatty alcohols with alkanoic acids with a low C number or with fatty acids;
• - alkyl benzoates;
• - Silicone oils, such as dimethylpolysiloxanes, diethylpolysiloxanes, diphenylpolysiloxanes and mixed forms thereof.

The oils in the sense of the present invention are advantageously selected from the Group of esters from saturated and / or unsaturated, branched and / or unbranched alkane carboxylic acids with a chain length of 3 to 30 carbon atoms and saturated and / or unsaturated, branched and / or unbranched alcohols Chain length from 3 to 30 carbon atoms, from the group of aromatic esters Carboxylic acids and saturated and / or unsaturated, branched and / or unbranched Alcohols with a chain length of 3 to 30 carbon atoms. Such ester oils can then advantageously selected from the group of isopropyl myristate, isopropyl palmitate, Isopropyl stearate, isopropyl oleate, n-butyl stearate, n-hexyl laurate, n-decyl oleate, isooctyl stearate, Isononyl stearate, isononyl isononanoate, 2-ethylhexyl palmitate, 2-ethylhexyl laurate, 2-hexyldecyl stearate, 2-octyldodecyl palmitate, oleyl oleate, olerlerucate, erucyl oleate, erucylerucate as well as synthetic, semi-synthetic and natural mixtures of such esters, for Example jojoba oil.

Furthermore, the oils can advantageously be selected from the group of branched and unbranched hydrocarbons and waxes, the silicone oils, the dialkyl ethers, the Group of saturated or unsaturated, branched or unbranched alcohols, as well as the fatty acid triglycerides, especially the saturated and / or triglycerol esters unsaturated, branched and / or unbranched alkane carboxylic acids Chain length of 8 to 24, especially 12 to 18 carbon atoms. The fatty acid triglycerides can for example advantageously selected from the group of synthetic, semi-synthetic and natural oils, for example olive oil, sunflower oil, soybean oil, Peanut oil, rapeseed oil, almond oil, palm oil, coconut oil, palm kernel oil and the like.

Any mixtures of such oil and wax components are also advantageous in To use the sense of the present invention. It can also if necessary be advantageous to use waxes, for example cetyl palmitate, as the sole component.

The oils are advantageously selected from the group consisting of 2-ethylhexyl isostearate, octyldodecanol, isotridecyl isononanoate, isoeicosane, 2-ethylhexyl cocoate, C _12-15 alkyl benzoate, caprylic capric acid triglyceride and dicaprylyl ether.

Mixtures of C _12-15 alkyl benzoate and 2-ethylhexyl isostearate are particularly advantageous; Mixtures of C _12-15 alkyl benzoate and isotridecyl isononanoate and mixtures of C _12-15 alkyl benzoate, 2-ethylhexyl isostearate and isotridecyl isononanoate.

Of the hydrocarbons, paraffin oil, squalane and squalene are advantageous in the sense of to use the present invention.

So that an adhesive based on natural rubber latex can be easily manufactured and can be processed, it is necessary to use a suitable adhesive To provide defoamers. Particularly suitable for adhesive based Natural rubber latex has the use of defoamers based on organomodified polysiloxanes proven.

Defoaming additives based on organomodified polysiloxanes show on the one hand an excellent, foam-destroying effect, and at the same time the Adhesive based on natural rubber latex a crater-free wettability of the Carrier surface based on polypropylene. All others mentioned show this behavior Do not defoamer.

For the adhesive tapes according to the invention, organomodified polysiloxanes are used as Defoamer used. The adhesive contains in particular 0.001 to 3.0% by weight of one Defoamer based on organomodified polysiloxanes. In one particularly preferred embodiment, the adhesive contains 0.01 to 1.0 wt .-% of a defoamer based on organomodified polysiloxanes. The use is also according to the invention of mixtures of different, organomodified polysiloxanes.

Polysiloxanes are oxygen compounds of silicon of the general formula H ₃ Si [O-SiH ₂ ] _n -O-SiH ₃ . If the hydrogen atoms are replaced by organic radicals, the compounds are referred to as polyorganosiloxanes. Silicones are systematically referred to as polyorganosiloxanes.

All the partially halogenated silanes, like the fully halogenated silanes, are submerged by water Formation of oxygen derivatives of monosilane quickly decomposes. First of all The hydrolysis products formed are, however, unstable and condense with the escape of water to siloxanes or polysiloxanes. This leads to curled Ring or cage structures. Exactly how the siloxane base bodies are also by exchanging the water atoms with organic groups "organomodified" Siloxanes can be represented. These organo-modified siloxanes are used as defoamers Example used in PVC production or serve as defoaming additives in the Textile industry. In particular, organomodified siloxanes are used wherever conventional silicones are not used or only to a limited extent.

Defoamers based on organomodified polysiloxanes can use the aqueous adhesive are added at any time of the formulation and are substances that are on the Interface liquid-gaseous form a closed film and thereby to it allow degassing medium in a very short time while destroying the gas bubbles to form the smallest surface and thus the low-energy state.

Anti-aging agents for adhesives based on natural rubber are known. Three Various types of anti-aging agents are found as antioxidants for adhesives especially use. Anti-aging agent based on amines, dithiocarbamates and based on phenols. Anti-aging agents based on phenols are very effective under the influence of UV radiation and sunlight.

For the adhesive tapes according to the invention, anti-aging agents based on Phenols used. The adhesive contains in particular 0.1 to 5% by weight of one Anti-aging agent based on phenols. The use is also according to the invention other types of anti-aging agents, such as anti-aging agents Base of amines and dithiocarbamates.

Inorganic and organic pigments for adhesives based on natural rubber are known. For the coloring of adhesives based on natural rubber in particular titanium dioxide or titanium dioxide in combination with differently colored ones Color pigments used.

Suitable inorganic and / or organic color pigments used in dispersion form. The adhesive contains preferably 0.05 to 20% by weight of an organic or inorganic Color pigment. The use of pigments based on Mixtures of various inorganic and organic pigments.

Natural rubber latex can counteract by using suitable stabilizers mechanical shear forces are stabilized and thus the tendency to coagulate be reduced or excluded. Suitable stabilizers are Additives based on potash soaps of synthetic carboxylic acids. Also as stabilizers are known ethoxylates with a degree of ethoxylation greater than 30.

The adhesives according to the invention can contain 0.05 to 10% by weight of suitable stabilizers contain.

The adhesive tapes according to the invention can be produced by the known processes respectively. An overview of common manufacturing processes can be found, for example, in "Coating Equipment", Donatas Satas in "Handbook of Pressure Sensitive Adhesive Technology ", Second Edition edited by Donatas Satas, Van Nostrand, New York, pp. 708-808. The known methods for drying and cutting the adhesive tapes are also in the Find Handbook.

The adhesive tapes of the invention are for a large number of Suitable for tape applications. Packaging applications are an important field of application. The Adhesive tapes are suitable as cardboard tape, general Packaging tapes, strapping tapes, adhesive tapes for sealing plastic packaging and Plastic bags. The adhesive tapes are suitable for securing pallets. Further Applications are the bundling of loose goods and transport goods, such as pipes, Wooden strips u. a. The adhesive tapes of the invention can be used to secure the transport of for example refrigerators and other electrical and electronic devices be used. Other applications are label protection, surface protection, for example in the construction sector, and tear strips for packaging. Likewise are Applications in the office area possible.

The packaging tapes in particular have run lengths of 66, 100 and 1000 m. 18, 24, 36, 48, 50 and 72 mm are usually selected as the width of the rolls.

The preferred colors are brown, white and transparent. The printing is done on rolls of 144 or 150 mm width, which then again to the above widths get cut.

The rolling noise is according to an excellent embodiment of the invention in 25 cm Distance to the adhesive tape less than 80 dB (A).

In the following, the invention will be explained using examples, without the invention want to limit unnecessarily.

Examples Example a) foil

A biaxially stretched film based on polypropylene from Radici is used:

Film thickness: 28 µm
Marking: Radil T
Company: Radici SpA
Elongation at break: 130%
Elongation at break across: 50%
Elastic modulus along: 2500 N / qmm
Elastic modulus across: 4000 N / qmm

The surface energy of the untreated Radil T25 BOPP film is less than 30 mN / m. The surface energy of the polypropylene surface with the adhesion promoter is 44 to 46 mN / m after corona treatment.

The surface energy of the untreated polypropylene surface of the Radil T25 film is less than 30 mN / m. This is the side of the film opposite the adhesive.

Example b) components Components used

• 1. b1 of the adhesive
  • 1. b1.1 natural rubber latex, obtainable from Weber & Schaer, Hamburg, (solids content 60%)
  • 2. b1.2.1 Aqueous resin dispersion based on hydrocarbon resins (Hercules BV, Tacolyn 1070, solids content 55% by weight; softening point 70 ° C.)
  • 3. b.1.3 Anti-aging agent Lowinox 2246 from the Great Lakes, USA
  • 4. b1.4 defoamer TEGO Antifoam 288 from Goldschmidt, Essen
  • 5. b1.5 Dicera 11833, oil dispersion from Paramelt, NL
• 2. b2 of the primer
  • 1. b2.1 Trapylen 6965W (low chlorinated polypropylene dispersion from Tramaco, Hamburg), or Butofan LS103 (styrene-butadiene dispersion from BASF)

Example c) recipes

• 1. c1 formulation A of the adhesive

• 1. c2 Rezeptur B des Primers

The recipe is given in% by weight:
Natural rubber latex dispersion 47.0% by weight Tacolyn 1070 47.0% by weight Dicerra 11833 5.0% by weight Anti-aging agents 0.7% by weight TEGO anitfoam 288 0.3% by weight

• 1. c2 recipe B of the primer

The recipe is given in% by weight:
Trapylen 6965W 100% by weight Or Butofan LS103 100% by weight

Example d) Production of the adhesive and the primer

• 1. d1 In die Naturkautschuklatex wird bei 23°C die Harzdispersion unter ständigem Rühren mit einem üblichen mechanischen Rührer zugegeben. Danach wird 15 min weiter vorsichtig gerührt.
• 2. d2 In die Mischung von Schritt 1 (d1) wird vorsichtig das Alterungsschutzmittel und der Entschäumer eingerührt. Danach wird 15 min weitergerührt.
• 3. d3 In die Mischung von Schritt 2 (d2) wird vorsichtig die Öldispersion eingerührt. Danach wird 15 min weitergerührt. Danach erfolgt die Beschichtung.

The adhesive compositions A to be coated are produced as follows:

• 1. d1 The resin dispersion is added to the natural rubber latex at 23 ° C. with constant stirring using a conventional mechanical stirrer. Then stirring is continued for 15 minutes.
• 2. d2 The aging inhibitor and the defoamer are carefully stirred into the mixture from step 1 (d1). Then stirring is continued for 15 min.
• 3. d3 The oil dispersion is carefully stirred into the mixture from step 2 (d2). Then stirring is continued for 15 min. Then the coating takes place.

• 1. d4 Trapylen 6965 W und Butofan LS103 werden ohne weitere Vorbehandlung vermischt und eingesetzt.

The primer with formulation B is prepared as follows:

• 1. d4 Trapylen 6965 W and Butofan LS103 are mixed and used without further pretreatment.

Example e) coating

The coating of the film a) with the primer formulation B and the adhesive formulation A done by a wire squeegee. In a first step, the primer is applied, briefly dried at 80 to 90 ° C and immediately afterwards in a second step (in-line or off- line) the adhesive is applied to the primer layer.

The wire doctor blade and the coating speed are set so that after the Drying of the coated film a mass application of about 18 g / sqm is measured and a primer application of 0.6 to 0.8 g / qm is measured. The coating was carried out on a Technical coater with a working width of 500 mm and one Coating speed of 10 m / min. Behind the coating station with Wire knife applicator there is a drying tunnel that is operated with hot air (approx. 100 ° C). The coated film was made up to a width of 50 mm and a length of 60 m.

The adhesive data were determined after two days of storage at 23 ° C and after storage for one to three months at 23 ° C.

Example f Results

The test methods used are briefly characterized below:
To determine the application of mass, a circular pattern with a known surface area is cut out of the coated film and weighed. The adhesive is then removed by removing it with petrol and the film, which is now free of adhesive, is weighed again. The mass application in g / m ^{2 is} calculated from the difference.

To characterize the handling of cardboard, the adhesive tape is used with a commercial hand dispenser applied to the box and by means of a 2 kg heavy Pressed steel roller (roll over twice). After a waiting time of 3 min Adhesive tape at a speed of approx. 30 m / min at an angle of approx. 130 ° to the Cardboard surface peeled off in parallel. The assessment of the handling of cardboard is done qualitatively based on the amount of torn paper fibers compared to one commercially available packaging adhesive tape, such as tesapack 4124 from Beiersdorf, whose Touch is very well characterized.

To determine packaging security, a standard box (shipping box; 425 mm × 325 mm × 165 mm: length × width × height: Europakarton; built up from double-wall corrugated cardboard with 125 g / m² outer layer made of kraftliner) with the adhesive tape using a commercially available packaging machines (from Knecht, model 6030 and sealing unit 6230, setting without braking distance) closed. The adhesive tape is centered in the usual U- Closure applied so that 60 mm of adhesive tape are glued to the end faces. The carton is completely filled with peas before sealing and on the side surface stored horizontally at 40 ° C and at 23 ° C. The packaging security is very good characterized if the box remains closed for more than 30 days. Furthermore, that will Slipping of the adhesive tape on the box or the behavior of the adhesive tape the glued areas characterized and described and with the reference tape compared (Table 1).

The unrolling noise is determined when the adhesive tape is unrolled with a Unwind speed of 45 m / min. Rolling noise is measured in dB (A) at a distance 25 cm from the center of the tape roll with a standard volume meter from Brüel & Kjear (Type 2226). A measured volume is less than 80 dB (A) classified as quiet.

The unwind force is measured at a constant unwind speed (30 m / min) Measurement of the torque and calculation of the rolling force according to the known formulas in N / cm.

The effectiveness of the defoamer is measured by measuring the foam height, after the formulation to be examined 5 minutes at 1200 r. p. m. is stirred. After that the foam height is measured in millimeters.

The measurement of the wettability and crater formation of the adhesives used in Dependency of the defoamer on carriers based on polyolefins becomes visual estimated. Here, the adhesive is applied to a surface of untreated Polyolefins or primed polyolefins distributed as a thin film and the crater formation 1 assessed up to 2 minutes. If after 1 to 2 minutes no craters respectively If wetting problems arise, the sample is assessed as good.

The assessment of the suitability of organomodified polysiloxanes as defoamers for aqueous adhesives, in particular based on natural rubber latex, in comparison with conventional defoamers is shown in Table 1. Table 1 Comparison of defoamers

(Defoamers A and B, see Table 1, are used as standard defoamers in the Example included. The effectiveness and overall performance of the defoamer is here very strongly dependent on concentration. The standard concentration was 0.3% by weight Defoamer accepted, see recipe A, example c1.)

The results of the examination of an adhesive tape according to the invention with an embossed film and the assessment of comparison adhesive tapes are shown in Table 2. Table 2 Behavior of the adhesive tapes according to the invention

Claims (10)

1. Self-adhesive tape on one side, with: a) a film based on thermoplastic polymers, b) an adhesive layer applied to the film on one side, produced from a mixture comprising:
35 to 69.5% by weight of a natural rubber latex
20 to 64.5 wt .-% a resin dispersion based on a hydrocarbon resin
0.5 to 20% by weight of an oil-based additive
0.001 to 3 wt .-% of a defoamer based on an organomodified polysiloxane 2. Adhesive tape according to claim 1, characterized in that the film is stretched There is polyolefins and / or a film thickness between 20 and 50 microns. 3. Adhesive tape according to claim 1 or 2, characterized in that the film made of biaxial stretched films based on polypropylene and / or a film thickness between 15 and 100 microns, in particular between 25 and 50 microns. 4. Adhesive tape according to one of claims 1 to 3, characterized in that the film consists of monoaxially stretched films based on polypropylene and / or one Has film thickness between 25 and 200 microns, in particular between 40 and 130 microns. 5. Adhesive tape according to at least one of the preceding claims, characterized characterized in that a layer of a primer between the film and the adhesive layer is applied. 6. Adhesive tape according to at least one of the preceding claims, characterized characterized in that the layer application of the adhesive layer on the film is 10 to 45 g / qm. 7. Adhesive tape according to at least one of the preceding claims, characterized in that the adhesive is added, chosen independently of one another:
0.1 to 5% by weight of an anti-aging agent
0.05 to 20% by weight of at least one color pigment and / or
0.05 to 10% by weight of a stabilizer 8. Adhesive tape according to at least one of the preceding claims, characterized characterized in that anti-aging agents based on phenols are added to the adhesive are, in particular 0.1 to 5 wt .-%. 9. Adhesive tape according to at least one of the preceding claims, characterized characterized in that the rolling noise at 25 cm distance to the tape is less than Is 80 dB (A). 10. Use of the adhesive tape according to one of claims 1 to 9 as Packaging adhesive tape, with good grip on paper, in particular recycled paper, sufficient cohesion, good packaging security, good anchorage and easy rolling.